The trouble with primer is that one of its propertys is its porous
if you leave your chassis for any length of time in just primer it will rust under the primer and you wont see it till its getting bad
if you want it to remain rust free you have to put a top coat on in a reasonable amount of time
or if your using a spray gun add some topcoat to the primer this will stop or minimse the porosity and hopefully stop invisible rusting
Ray
